The present invention relates generally to the air brakes used for railroad cars. It particularly relates to the flexible hose assemblies between adjacent cars in a train that provide an integral air connection throughout the length of the train. This is referred to by railroad persons as the "brake pipe." This "brake pipe" carries air that is pumped through the length of the train by a compressor in the locomotive. The fail safe feature of the air brake system is provided by filling the air storage vessels located on each car in the train to a predetermined pressure level. The brake control valve on each car will self-adjust into a brake release mode when the pressure of air in the air storage vessel on each car and in the control valve is at equilibrium with the pressure in the brake line. The train may then be propelled along the track by the locomotive as long as the air pressure in the brake pipe is within a small difference in pressure with the pressure in the air storage vessel on the individual cars of the train. The brakes can be applied by the engineer lowering the air pressure in the brake pipe in fixed proportion to the braking force desired. An emergency brake application can be created, when desired, by rapidly reducing the air pressure in the brake pipe.
A fail safe emergency brake application will be automatically created if the integrity of the brake pipe is broken. The unintentional disconnection or uncoupling of two hose assemblies between adjacent cars will result in rapid loss of air pressure in the brake line. This in turn causes all the brakes on the cars of the train to apply with maximum force.
Individual hose couplings are designed to facilitate rapid manual assembly and disassembly. The coupling together of two adjacent hose assemblies is achieved by manually raising and rotating the coupling ends of the two hoses so that the guard arm and lip of one coupling can be moved into the same plane as the lip and guard arm of the adjacent coupling. The hose coupling ends are then rotated downward so that the lip bead of each coupling will enter the groove of the guard arm on the mating coupling. Rotation of the two couplings will continue until the guard arm of each coupling contacts the stop lug of the mating coupling. The guard arms and lips of mating couplings are provided with ramps that cause the couplings to exert a compressive force on the coupling gaskets in the mating faces of the couplings. The compressed gaskets will prevent leakage of air from the coupled air hose assemblies. Gravity and the forces induced by the bent condition of the two hose assemblies will normally retain the couplings in the interlocking mode.
A counter-rotating motion created by manually raising the hose assemblies will allow the couplings to be disconnected. A similar counter-rotation motion can be induced by the vertical movement of the hose assemblies resulting from the oscillations and lurching of the car bodies during train operations. At such occasions of unintentional hose separation, the brakes are simultaneously applied at full force and the train quickly decelerated to a stop. An emergency application of brakes during a high speed train operation may result in the wearing of flat spots on the wheels, and damage to lading or injury to livestock or passengers.
In an effort to address this problem, the industry has provided hose couplings with unitary mechanisms to prevent the uncoupling of a pair of air hose couplings. Specially designed air hose couplings having an integral latch are illustrated in U.S. Pat. Nos. 3,892,431; 4,129,323; and 4,125,279. Although such prior art devices provide a latch or other device to prevent undesirable uncoupling, they do require specially designed air hose couplings. This is uneconomical. Similarly, such devices provide no solution to the undesirable uncoupling of air hose couplings which are presently in use.
Prior art devices are available which are attachable to preexisting air hose couplings and to serve as latching means for preventing uncoupling thereof. A typical example is U.S. Pat. No. 3,941,254. The locking means is a wire form which can be secured to the air hose coupling and form an integral part thereof. The locking means provides a shoulder parallel to the axis of rotation of the coupling to engage the side of a lip and coact with another portion which engages the housing of the other air coupling to provide a lock. Although providing a device which may be used with preexisting air hose couplings, the particular configuration of U.S. Pat. No. 3,941,254 is subject to misalignment during the motion of the train and consequently cannot ensure that the locking shoulder is always in place. Also the locking wire form is not readily positioned on the coupled air hose couplings.